1. Field of the Invention
The present invention relates to an improvement in a supporting device of a head rest for a vehicle seat, in which the head rest is vertically adjustably supported by a frame of the back portion of the seat.
2. Description of the Prior Art
Conventionally, in order to enable an adjustment of the height of the head rest, the head rest is provided with a pair of parallel supporting rods which are inserted into the seat back and retained at a desired adjusted height. To this end, a supporting device is known which includes a latch member selectively engageable with one of notches forming a row extending longitudinally of the supporting rod. With this arrangement, however, the head rest is lifted or lowered stepwisely only so that a fine adjustment to obtain an optimum driving position cannot be achieved. Another type of supporting device is also known by which a stepless fine adjustment of the head rest can be made. Such a supporting device includes a resilient member which is always in frictional contact with the supporting rod without notches. In this case, in order to adjust the height of the head rest, the head rest has to be lifted or lowered against the frictional force of the resilient member so that a substantial adjusting force is required.